Currently, in an injection-enhanced insulated gate bipolar transistor (IGBT), the buffer layer is formed by generally implanting an N-type dopant, and then a drive-in is performed, a body implantation is performed, then a drive-in is performed again, such that a time period of the drive-in for forming the buffer layer is longer than a time period of the drive-in for forming the body, which results in that a junction depth of the N-type dopant to be deeper than a junction depth of the body. Therefore, when such IGBT manufacturing method is adopted, it requires an additional drive-in to the buffer layer before performing a drive-in to the body, the N-type dopant is distributed and diffused by virtue of a long time period of drive-in, causing the junction depth of the N-type dopant to be deeper than the junction depth of the body, an N+ is formed beneath the body, such that an enhanced injection can be achieved. However, the method of manufacturing the injection-enhanced IGBT requires additionally adding a drive-in process, the production cycle thereof is long.